INTRODUCTION 



One of the serious problems confronting the conservation author- 

 ities responsible for protecting and developing shad fisheries is the 

 construction of satisfactory fishways. The reluctance of shad to enter 

 and to ascend most fish ladders has usuallj r resulted in the shad being 

 completely cut off from all of the natural spawning areas above the 

 first dam encountered in their upstream migration. The passage of shad 

 through the fishways at Bonneville Dam on the Columbia River is a nota- 

 ble exception, although even in the fishways at Bonneville Dam the shad 

 are not always successful in ascending]/- However, it is difficult to 

 find in the enormous fishway system at 1 Bonneville, with its pools hO 

 feet in width, its auxiliary water supplies and its huge collecting 

 system, a solution to the problem which would be applicable to the 

 smaller, privately owned dams with which those interested in shad fish- 

 eries on the Atlantic Coast are largely concerned. Another fishway, 

 not very well known, which shad ascend successfully is the fishway at 

 the Essex Company Dam on the Merrimack River at Lawrence, Mass. For 

 the consideration of those concerned with the design of suitable fish- 

 ways for shad the distinctive features of the fishway, reputed to be 

 the only fishwav on the East Coast successfully passing shad, are out- 

 lined here. 



HISTORY AND DESCRIPTION OF FISHWAY 



The fishway at the Essex Company Dam in Lawrence was built in 

 1919 at a cost of $28,000. Because several previous fishways had been 

 destroyed by ice the fishway was heavily constructed and located in its 

 present position so as to have a minimum of exposure. The fishway has 

 a total of hi pools to overcome a maximum difference in elevation of 

 30 ft. between the forebay and tailwater. The lower 36 pools are 8 ft. 

 by 8 ft. and are arranged in pairs (Figure 1) . There is a drop of 0.6 ft. 

 between pools (Figure 2) although when the fishway is in operation some 

 of this difference is taken up by the slope of the water in the pools so 

 that the actual difference at the weirs is only about 0.1; ft. The weirs 

 are notched and are unusually thick (1 ft.). The fishway narrows at the 

 top into single pools which are only 6.3 ft. wide but are approximately 

 10 ft. in length. The upper 9 pools have adjustable plank weirs to ac- 

 commodate the fishway to fluctuations in forebay level. 



_/ "Passage of Fish over Bonneville Dam" Annual Report, Corps of Engi- 

 neers, U. S. Army, 19^9. 



